Purpose: Recent studies developed a 1h algorithm for rapid rule-out and rule-in of Acute Myocardial Infarction (AMI) based on high-sensitivity cardiac troponin T testing. We aimed to extend these findings and to assess whether a similar 1h algorithm can also be derived using a sensitive cardiac troponin I (s-cTnI) assay.

Methods: In a prospective international multicentre study we enrolled 912 consecutive patients presenting to the Emergency department (ED) with acute chest pain. S-cTnI (Beckman Coulter) was measured at presentation and after 1h in a blinded fashion. The final diagnosis was adjudicated by two independent cardiologists. An algorithm including the baseline s-cTnI values as well as absolute changes within the first hour was developed for early rule-in and rule-out of AMI.

Results: Among all patients 18% had a final diagnosis of AMI. The rule-out criteria of our algorithm were defined as baseline s-cTnI level lower than 0.009ug/l and an absolute change within the first hour of less than 0.005ug/l, and the rule-in criteria were defined as baseline s-cTnI level of 0.070ug/l or higher or an absolute change within the first hour of 0.015ug/l or higher. Applying the algorithm 50% patients could be classified as rule-out, 20% patients as rule-in, and 30% as in an observational zone. Overall, this resulted in a sensitivity and negative predictive value (NPV) of 97.8% and 99.2% respectively for rule-out, and specificity and positive predictive value (PPV) of 95.1% and 75.0%, respectively for rule-in, and an AMI prevalence of 9% in the observational zone group.

Conclusion: Using the novel algorithm based on s-cTnI baseline values and absolute changes within 1 hour allows a safe rule-out and an accurate rule-in within 1h in 70% of unselected patients with acute chest pain. The NPV is only slightly lower as compared to the use of hs-cTnT.